Altn Proc.,
The company isn't charging Mr Airmen for the groundschool. They're charging (or at least trying to) him for breaking a trainingbond.
They can argue that they've paid the flighttraining establishment for the course and now, that place on the course will be wasted. It's a whole different matter, that they most likely WILL fill that spot with someone else. They're just out trying to make some easy cash and since Airmen signed a bonding agreement, they have a pretty good case.
Airmen,
If I were you, I'd get in contact with a solicitor/lawyer/word-bender immediately. Hopefully you will get away.....
Good luck mate! Fight them!